Generally, the art of prosthesis is old and many attempts have been made to achieve endoskeleton prosthesis which restores function and is also provides cosmetically aesthetic appearance. Artificial limbs that reproduce natural movement are desired so the user can function normally in society performing typical daily tasks and routines at both work and home. In the United States attempts to make acceptable prosthetic devices date back to the 1800's as illustrated in U.S. Pat. No. 168,140 "Artificial Leg" to Collins and McCalla (1875); No. 489,258 "Artificial Limb" to Marks (1893); No. 453,285 "Artificial Leg" to Kneider (1891); No. 492,583 "Artificial Leg Attachment" to Duffie (1893); No. 909,859 "Artificial Leg" to Apgar (1909); No. 1,216,367 "Artificial Leg" to Rowley (1917); No. 1,314,136 "Artificial Leg" to Gaines and Erb (1919); No. 1,370,299 "Artificial Limb" to Flanagan (1921); No. 5,139,526 "Long Above Elbow and Elbow Disartic Prosthesis" to Skardoutos et. al (1992), and No. 5,226,918 "Prosthesis with Adjustable Fitting Clearance" to Silagy and Lenze (1993). As people with disabilities are becoming increasingly active in today's society, continued efforts are being made to develop more functional artificial limbs.
For leg amputations, prior art prosthesis devices have mainly been designed for amputations which occur below the knee as exemplified in a number of the above listed US Patents. Since the knee joint is left in tack, it still has functionality and the prosthesis merely replaces the lower leg portion typically with an artificial leg shin and foot. While factors such as weight and leg attachment must still be addressed to create a natural working lower leg, the knee joint is still used to provide the pivotal point for the lower leg and simplifies the prosthesis design. However, for the most part prior art including the aforementioned prior art patents do not provide an adequate prosthesis solution for the particular problems that arise for amputation at or just above the knee. Such amputations either disable the knee joint or take it out altogether, and therefore a properly functional prosthesis device must include a suitable arrangement that substitutes for the former knee.
A conventional prosthesis to accommodate a leg stump of an amputee which attempts to incorporate a knee joint arrangement is illustrated in FIGS. 1 and 2, which prosthesis includes an upper leg socket section 20 for receiving a leg stump and a lower leg section 22. The upper leg socket section is attached to the lower leg section by knee joint 24. The knee joint 24 rotates or swings about the knee axis 26 which is established in the knee joint 24 by knee axis bolt 28 which pivotally couples the upper and lower leg sections. As the knee joint 24 is connected near the bottom of the upper leg socket section 20, the knee axis 26 may end up as much as about 21/2 to 31/2 inches below the bottom of the leg stump. Additionally, since the knee joint side attachments depend on a single axis bolt to create the knee joint pivot, a properly aligned knee axis pivot is difficult to achieve.
While most prior art leg prosthetic arrangements, such as the examples listed above, are fine for short or mid-length femur amputations, these arrangement typically result in several functional and cosmetic problems for long femur and knee disarticulation amputations. Functionally, it results in an awkward stride length, stride timing, and gait pattern for the amputee, and thus a natural appearing walk is not possible. Cosmetically, this arrangement results in a longer than desired leg thigh section and corresponding short shin section. This looks unpleasant while the amputee is in a sitting position, as the prosthetic knee sticks out further that the sound knee and the short shin section may leave the foot swinging in the air when it does not reach the ground. Furthermore, while walking the shin section has less weight and shorter pendulum swing, resulting in an undesirable swing period which does not match the sound side leg. Patients do not desire a prosthesis with these shortcomings and an improved leg prosthesis without the foregoing disadvantages would provide a desirable advancement in the prosthesis art. It should be noted that a knee disarticulation amputation, if possible, provides a much more solid support for a prothesis than an amputation of the femur. Amputation of the femur leaves only a small diameter of bone end for support as contrasted to the relatively large bone mass at the knee joint.